• Journal of Power Electronics
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• v.11 no.6
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• pp.914-921
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• 2011

Commencing with incandescent light bulbs, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and their response to problems caused by harmonics. The prevalent difficulties with harmonics are voltage and current waveform distortions. In addition, Electronic equipment like computers, battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies generate perilous amounts of harmonics. Issues related to harmonics are of a greater concern to engineers and building designers because they do more than just distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality is becoming more and more serious with each passing day. As a result, active power filters (APFs) have gained a lot of attention due to their excellent harmonic compensation. However, the performance of the active filters seems to have contradictions with different control techniques. The main objective of this paper is to analyze shunt active filters with fuzzy and pi controllers. To carry out this analysis, active and reactive current methods ($i_d-i_q$) are considered. Extensive simulations were carried out. The simulations were performed under balance, unbalanced and non sinusoidal conditions. The results validate the dynamic behavior of fuzzy logic controllers over PI controllers.

• ETRI Journal
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• v.44 no.2
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• pp.260-273
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• 2022

This study presents a novel multilayer structure of parallel coupled-line bandpass filtercentered at 2.42 GHz with a fractional bandwidth value of approximately 19.4%. The designed filter can suppress harmonics with an appropriate frequency response by incorporating different techniques based on the multilayer technique. A combination of different techniques such as radial microstrip stubs and defected ground structure (DGS) and defected microstrip structure techniques are employed to suppress harmonics up to 5f₀. These techniques are used in two layers to suppress up to 5f₀. In addition, in this study, the effects of different parameters, such as the width of slot-line DGS, the angle of diagonal line slots in the upper layer, and the air gap between the two layers on the filter performance, are investigated. To verify the correct circuit operation, the designed filter is implemented and tested. The measurement results of the proposed filter are compared with the simulation results.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1621-1625
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• 2015

Power quality has always been a concern of power engineers. Certainly an argument can be successfully made that most parts of power engineering have the ultimate objective to improve power quality. AC motors were widely used in industrial and domestic applications. Generally, AC motors were of two types: Induction and Synchronous motors. In motor many parameters like different load cycling, switching, working in hot weather and unbalances creates harmonics which creates major reasons for temperature rise of the motors. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Based on the previous project works, actions were taken to use the enamel filled with various nano fillers for the coating of the windings of the different AC motors. Ball mill method was used to convert the micro particles of Al₂O₃, SiO₂, TiO₂, ZrO₂ and ZnO into nano particles. SEM, TEM and XRD were used to augment the particle size of the powder. The synthesized nano powders were mixed with the enamel by using ultrasonic vibrator. Then the enamel mixed with the nano fillers was coated to the windings of the several AC motors. Harmonics were measured in terms of various indices like THD, VHD, CHD and DIN by using Harmonic analyzer. There are many other measures and indices to describe power quality, but none is applicable in all cases and in many instances, these indices may hide more than they show. Sometimes power quality indices were used as a basis of comparison and standardization. The efficiency of the motors was increased by 5 – 10 %. The thermal withstanding capacity of the motor was increased by 5º to 15º C. The harmonics of the motors were reduced by 10 – 50%.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.3861-3878
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• 2021

The steady-state simplified spherical harmonics equations (SP_N equations) are a higher order approximation to the neutron transport equations than the neutron diffusion equation that also have reasonable computational demands. This work extends these results for the analysis of transients by comparing of two formulations of time-dependent SP_N equations considering different treatments for the time derivatives of the field moments. The first is the full system of equations and the second is a diffusive approximation of these equations that neglects the time derivatives of the odd moments. The spatial discretization of these methodologies is made by using a high order finite element method. For the time discretization, a semi-implicit Euler method is used. Numerical results show that the diffusive formulation for the time-dependent simplified spherical harmonics equations does not present a relevant loss of accuracy while being more computationally efficient than the full system.

• Journal of Magnetics
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• v.6 no.2
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• pp.66-69
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• 2001

The actual magnetic induction waveform of cores in electrical machines is not sinusoidal i.e. higher harmonics are always included. Thus the core loss in actual electrical machines is different from the core loss which is measured by the standard method, because the waveform of magnetic induction should be sinusoidal in the standard testing method. Core loss analysis under higher harmonic induction is always important in electric machine design. In this works we measured the core loss when a hysteresis loop has only one period of an ac minor loop of higher harmonic frequency, depending on the position of the ac minor loop of relative to the fundamental harmonic frequency. From this experiment, the core loss P(B/sub 0/f/sub 0/, B/sub h/, nf/sub 0/)) under a higher harmonic magnetic induction B/sub h/ could be expressed by the linear combination the core loss at fundamental harmonic frequency P/sub c/(B/sub 0/, f/sub 0/), the core loss of ac minor loop at zero induction region of the major hysteresis loop P/sub cL/ (B/sub h/, nf/sub 0/), and the core loss of an ac minor loop in the high induction region of the major hysteresis loop P/sub cH/ (B/sub h/, nf/sub 0/) i.e., P/sub c/, (B/sub 0/, f/sub 0/, B/sub h/, nf/sub 0/)=P/sub c/ (B/sub 0/, f/sub 0/,)+(n-1)[k₁(B/sub 0/) P/sub cL/ (B/sub h/, nf/sub 0/)+(1-k₁(B/sub 0/)) P/sub cH/ (B/sub h/, nf/sub 0/)]. This will be useful formula for electrical machine designers and one of effective methods to predict core loss including higher harmonic induction.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.282-284
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• 1997

The harmonics are injurious on the operation of the motor, electric instruments etc. In this paper, it is certified the capability of the electric measuring devices at the input/output of inverter. And it is measured the harmonics of the voltage and current waveforms. Also, this paper presents the efficiency of the inverter's power conversion by measuring the fundamental and total power at the input, DC bus and output.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.3
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• pp.159-164
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• 2000

This paper treats the optimization of rotor construction in the permanent magnet synchronous motor (PMSM) for electric vehicle (EV). While the field system of PMSM has generally one magnet per pole, we replace the magnet into plural sub-magnets. The dimensions of each sub-magnet are determined by the concept of pulse width modulation (PWM). By adopting the proposed rotor construction, we can not only reduce the space harmonics of the air-gap field but also provide space for rotor bars (i.e., damper windings) around the direct-axis. From the investigation by hybrid EE-BE (coupled finite element and boundary element) method coupled with both electric circuit and motion equation, we verify that the construction is effective for practical use.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.435-441
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• 2017

Detecting an inter-harmonic accurately is not easy work, because it has small magnitude, and its frequency which can be observed is not an integer multiple of fundamental frequency. In this paper, a new method using filter bank system and adaptive predictor is proposed. Filter bank system decomposes input signal to sub bands. In adaptive predictor, inter-harmonic is detected with decomposed sub band signal as input, and error signal as output. In this scheme, input-output characteristic of adaptive predictor is notch filter, as predicted harmonic is canceled in error signal, so detecting an inter-harmonic can be possible. Magnitude and frequency of detected inter-harmonic is estimated by recursive algorithm. The performances of proposed method are evaluated to sinusoidal signal model synthesized with harmonics and inter-harmonics. And validity of the method is proved as comparing the inter-harmonic detection results to MUSIC and ESPRIT.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.6
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• pp.272-275
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• 2004

A balanced single side-band (SSB) mixer employing a sub-harmonic configuration is designed for up and down conversions in K-band. The designed mixer uses anti-parallel diode (APD) pairs to effectively eliminate even harmonics of the local oscillator (LO) spurious signal. To reduce the odd harmonics of LO at the RF port, we employ a balanced configuration for LO. The fabricated chip shows 12$\pm$2dB of conversion loss and image-rejection ratio of about 20dB for down conversion at RF frequencies of 24-27.5GHz. As an up-conversion mode, the designed chip shows 12dB of conversion loss and image-rejection ratio of 20 ～ 25 dB at RF frequencies of 25 to 27GHz. The odd harmonics of the LO are measured below -37dBc.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.134-137
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• 2019

A wide-bandwidth current controller is required for fast charging/discharging of super capacitor applications. Peak current mode is generally used to accomplish fast charging/discharging because this mode has fast response characteristics. However, the peak current mode control must have a slope compensation function to restrain sub-harmonics oscillation. The slope must be changed accordingly if the controlled output voltage is varied. However, changing the slope for every changed output voltage is not easy. The other solution, selecting the slope as the maximum value, causes a slow response problem to occur. Therefore, we propose a hybrid mode controller that uses a peak current and a newly specified valley current. Through the proposed hybrid mode control, the sub-harmonic oscillation does not occur when the duty is larger than 0.5 because of the fast response.